1. Field of the Invention
This invention relates to an electronically controlled variable semiconductor resistor, and more particularly to an electronically controlled variable semiconductor resistor facilitating multiplication processing of an analog signal, i.e., modulation, demodulation and frequency conversion of the analog signal.
2. Description of the Prior Art
Conventionally, a bipolar transistor or a field effect transistor, is used for a semiconductor variable resistance element used for processing an analog signal, and such a transistor is characterized in that the impedance between the collector and the emitter or between the drain and the source of the transistor changes by a base current or voltage between the gate and the source, and is often used as a variable attenuator.
However, between the aforesaid variable impedance (herein, the impedance between the collector and the emitter or between the drain and the source) and a control signal (herein, the base current or voltage between the gate and the source), there is no relationship with respect to the intensity which is given by an equation, whereby the aforesaid transistors are not suitable for a multiplication processing element for use with an analog signal.